Watch out, Google Wallet. There's a new mobile-payment service in the works.

A consortium of of retailers today announced that they have launched a mobile-commerce company, called Merchant Customer Exchange (MCX). Best Buy, Target, Wal-Mart, and Lowe's are among the many companies that have signed up for the initiative. The companies combine to generate a whopping $1 trillion in sales each year.

MCX is currently in the process of developing a mobile application that would allow customers to pay for purchases at participating retailers with their mobile devices. According to MCX, the app will work across "virtually any smartphone" and will automatically integrate consumer deals, promotions, and retail programs.

"MCX will leverage mobile technology to give consumers a faster and more convenient shopping experience while eliminating unnecessary costs for all stakeholders," Mike Cook, corporate vice president and assistant treasurer at Walmart said today in a statement. "The MCX platform will employ secure technology to deliver an efficiency-enhancing mobile solution available to all merchant categories, including retail stores, casual dining, petroleum and e-commerce."

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The retailers' move could spell trouble for Google's fledgling Wallet mobile-payment app. Google Wallet runs on Android-based devices and allows customers with certain smartphones to pay for purchases from the handset. Google Wallet has so far been slow to roll out. However, until now, it was facing few competitors.

With MCX on the way, Google might find it a bit more difficult to expand its offering. Google is forced to partner with merchants and credit card companies to get its service up and running. With so many major retailers signing on to MCX, they might not want to partner with Google on Wallet.

MCX hasn't said when it'll launch its application, but the company did say today that it plans to announce "additional merchants, as well as more details regarding its product offering and partners, in the weeks and months ahead."

CNET has contacted Google for comment on the MCX announcement. We will update this story when we have more information.